Olefin disproportionation

ABSTRACT

Olefins are disproportionated in the presence of a novel catalyst composition comprising (a) a conventional olefin disproportionation catalyst, (b) a Group IIIa metal, Group IIIa metal compound or mixtures thereof and (c) a carrier of at least 75 percent alumina. The novel catalyst has a long catalytic lifetime and good disproportionation activity.

O Umted States Patent 11 1 1 1 3,728,414 Helden et a1. [45] Apr. 17,1973 [54] ()LEFIN DISPROPORTIONATION 3,261,879 7/1966 Banks ..260/6833,457,320 7/1969 Stapp et a1 [75] lnvenmrs' Y Heme", Charles R 3,554,9241 1971 Kjttleman et a1 ..260/683 Kohll; Pleter A. Verbrugge, all ofAmsterdam, Netherlands FOREIGN PATENTS OR APPLICATIONS Assignee: Shell lC p y, New rk, NY. 1,096,200 12/1967 Great Britain ..260/683 [22] Filed:Sept. 14, 1970 Primary ExamlnerDelbert E. Gantz PP 72,161 AssistantExaminerC. E. Spresser Attorney-Howard W. Haworth and Martin S. Baer[30] Foreign Application Priority Data I v [57] ABSTRACT Feb. 27, 1970Netherlands ..7002795 Olefins are disproportionated in the presence of a52 11.8. C1. ..260/683 D, 260/666 A, 260/668 R, novel catalystcomposition compfising a Com/w 2 0/ 77 R, 2 0/ 0 R tional olefindisproportionation catalyst, (b) a Group 51 Int. Cl. ..C07c 3/62 Illametal. Group Illa metal p n or mixtures [58] Field of Search ..260/683D, 666 H, thereof and a carrier of at least 75 percent 260/677, 680, 668mina. The novel catalyst has a long catalytic lifetime and gooddisproportionation activity. 56 R f 1 e erences Cited 6 Claims, NoDrawings UNITED STATES PATENTS 3,424,813 l/l969 Breckoff et a]..260/683.2

OLEFIN DISPROPORTIONATION BACKGROUND OF THE INVENTION Reactions ofolefinic molecules in the presence of metal-containing catalysts toproduce other olefinic molecules are known in the art asdisproportionation. A typical olefin disproportionation process isillustrated by U.S. Pat. No. 3,261 ,879,-issued July 19, 1966, to Banks,wherein two similar molecules of an olefin react in the presence ofcertain catalysts to produce one olefin of a higher carbon number andone olefin of a lower carbon number. For example, propylenedisproportionates by the process of U.S. Pat. No. 3,261,879 to produceethylene and butylenes.

A variation of this olefin disproportionation process, which might betermed reverse disproportionation is illustrated by the NetherlandsPatent application 6514985 of British- Petroleum Company, Limited,published May 20, 1966, wherein, in one modification, molecules of twodissimilar olefins are reacted to form two molecules of a single olefinproduct, e.g., ethylene and 2-butene react to form propylene.

Another variation of the process, being conveniently termed ring openingdisproportionation to distinguish it from other variations, is disclosedby U.S. Pat. No. 3,424,811 of Shell Oil Company, issued Jan. 28, 1969,wherein a cyclic olefin and an acyclic olefin react to form a singleproduct molecule. For example, ethylene reacts with cyclopentene by ringopening disproportionation to produce 1,6-heptadiene.

The term olefin disproportionation process as herein employed is meantto include all variations of olefin disproportionation reactions.

A variety of catalysts have been employed for olefin disproportionationreactions. One type of olefin disproportionation catalyst is that ofTurner et al., British Pat. No. 1,054,864, which comprises a supportedheterogeneous catalyst composition of rhenium heptoxide on aluminumoxide. McGrath et al., British Pat. No. 1,159,056 disclose an olefindisproportionation catalyst composition comprisingrhenium heptoxide onalumina modified with alkali or alkaline earth metal ions. Anotherolefin disproportionation catalyst is that of Phillips Petroleum Co.,British Pat. No. 972,935, which comprises an oxide of molybdenum, anoxide of aluminum and, optionally, an oxide of cobalt. BritishPetroleum, British Pat. No.. 1,096,200, use an olefin disproportionationcatalyst comprising lanthanum oxide and alumina.

SUMMARY OF THE INVENTION It has now been found that a novel catalyst,having long catalytic life and good activity in the catalysis of olefindisproportionation reactions, is obtained by modifying a conventionalolefin disproportionation catalyst with a Group Illa element of atomicnumber 21 to 71 inclusive, and compounds or mixture thereof.

DESCRIPTION OF PREFERRED EMBODIMENTS The Olefinic Reactants. The processof the invention comprises contacting two olefinic reactants, which arethe same or are different olefins, and are acyclic olefins or are cyclicolefins, in the presence of the novel catalyst composition of theinvention.

One class of suitable acyclic olefinic reactants is represented by thefomula.(l):

It l(-( lllt (I) wherein the R independently is hydrogen or alkyl of upto 19 carbon atoms with the total number of carbon atoms of the acyclicolefin, which total is herein termed n,being no more than 40.

Illustrative of acyclic olefinic reactants represented by formula (I)are ethylene, propylene, l-butene, 2-butene, isobutene, 2-pentene,l-pentene, isopentene, 2- methylbutenel 2-methylbutene-2, l-hexene,2-hexene, 3-hexene, Z-methylpentene-l, l-heptene, 2- decene, 6-dodecene,3-tetradecene and lO-eicosene.

In general, the preferred acyclic olefins are olefins of up to 25 carbonatoms, more preferably of up to 15 carbon atoms, and especiallypreferred are linear acyclic internal monoolefins, i.e., those olefinswherein each atom of the carbon-carbon double bond is substituted with asingle R group.

One class of suitable cyclic olefinic reactants is represented byformula (11) wherein A is a divalent hydrocarbon moiety of from three toten carbon atoms and of up to three ethylenic double bonds which areportions of carbocyclic rings and is selected so that the carbon atomsdepicted in the formula (II) are members of a carbocyclic ring of atleast five carbon atoms. The total number of carbon atoms of the cyclicolefinic reactant of formula (II) which total is herein termed m, istherefore from five to twelve.

Illustrative monocyclic olefinic reactants of formula (II) includecyclopentene, cycloheptene, cyclooctene, cyclodecene,1,5-cyclooctadiene, 1,6-cyclodecadiene and 1,5 ,9-cyclododecatriene,whereas illustrative poly cyclic olefinic reactants are illustrated bybicyclo(2.2. l )hepta-2,5-diene, bicyclo(2.2.l )-hept-2- ene,tricyclo(4.2.1.0)non-7-ene, tricyclo(5.2. l .0)- deca-3,8-diene,bicyclo(2.2.2)oct-2-ene, bicyclo(2.2.2)octa-2,5-diene,bicyclo(3.3.0)oct-2-ene, dicyclopentadiene (3a,4,7,7a-tetrahydro-4,7-methanoindene), and quadricyclo-(2.2. l .2 0)non- 8-ene. Particularlysatisfactory results are obtained when the cyclic olefinic reactant is amonocyclic or a bicyclic olefinic reactant of up to two ethyleniclinkages and most preferred are the monocyclic, monoolefinic reactantsoffrom five to eight carbon atoms.

Another class of suitable olefinic reactants are polyolefinic compoundscontaining two or more nonconjugated double bonds. Illustrativepolyolefins are poly-1,4-butadiene, poly-1,4-isoprene and a copolymer ofstyrene and butadiene.

An additional class of suitable olefinic reactants are alkenes of eightto 16 carbon atoms of the formula:

wherein Ar is an aromatic radical, preferably hydrocarbon aromatic of upto 10 carbon atoms, and the R groups are as defined above. Preferredcompounds of this type are styrene and alpha-methylstyrene.

When two different olefinic reactants are employed in thedisproportionation process, the molar ratio of one olefinic reactant tothe other olefinic reactant is not critical, and up to a 20-fold excess,preferably up to a -fold excess of one olefinic reactant can be employed.

The Catalyst. The novel catalyst composition comprises (a) aconventional olefin disproportionation catalyst, (b) a Group llla metalor compound, or mixtures thereof, and (c) a carrier comprising at least75 percent alumina.

A stable catalyst with a greatly increased catalytic lifetime isproduced by modification of any conventional olefin disproportionationcatalyst with a Group Illa compound or element or a mixture of GroupIlla compounds or elements. The addition of the Group Illa modifier canresult in a tenfold or more increase in the active lifetime of thedisproportionation catalyst. Typical olefin disproportionation catalystsare compounds of a metal with atomic number 22 to 25, 40 to 46, 50 and72 to 77, that is, titanium, vanadium, chromium, manganese, zirconium,niobium, molybdenum, technetium, ruthenium, rhodium, palladium, tin,hafnium, tantalum, tungsten, rhenium, osmium and iridium. Compounds ofmolybdenum, tungsten, rhenium, iridium, and rhodium are particularlyactive with preference being given to molybdenum, tungsten and rhenium.

The compounds of a metal with atomic number 22 to 25, 40 to 46, 50 and72 to 77 may be organic compounds. Thus, such a compound may consist ofa salt of the metal concerned with an inorganic acid, or an organicacid, or an organic compound in which the metal concerned is part of acomplex, for instance, a 1r-ally1 complex. Preference is given to aninorganic comides and other compounds of Group Illa metals which caneasily be converted into oxides have proved very suitable. The optimumcontent of Group Illa within the catalyst depends in part on thespecific Group Illametal. The lifetime of catalysts with too small anamount of Group Illa metal on the carrier is relatively short. Catalystswith too large an amount of Group Illa metal on the carrier have arelatively low disproportionation activity. In general, quantities areused in the range of from 0.05 to 5%w, calculated as Group Illa metal oncarrier. Preferred are quantities of from 0.2 to 2.5%w.

The carriers used in the process according to the present inventioncomprise at least 75% by weight alupound of the metals with atomicnumbers 22, to 25,40

to 46, 50, 72 to 77, in particular to oxides, halides,

sulphates, phosphates and/or carbonyl derivatives of molybdenum,tungsten and rhenium, oxides of niobium and tantalum and halides,sulphates and/or phosphates of titanium, zirconium, niobium andtantalum. Rhenium heptoxide is particularly satisfactory, because itpromotes olefin disproportionation reactions at room temperatures.

Of course, it is possible to use mixtures of compounds of one or more ofthe metals with atomic numbers 2 2 to 25, to 46, 50 and 72 to 77.

The modifying component used in the olefin disproportionation catalystis an element of atomic number from 21 to 71 inclusive of Group Illa ofthe Periodic Table or a compound of such metal, or mixture thereof. Asemployed herein, Group Illa is defined by the long form of the PeriodicTable of Mendeleev as reproduced in Cotton and Wilkinson, AdvancedInorganic Chemistry, 2nd Revised and Augmented Edition, lntersciencePublishers, 1966. Preferred Group Illa metals are lanthanum, cerium,praseodymium, neodymium, samarium, europium and gadolinium. Particularlyac tive are cerium and europium. A mixture of rare earth metals in theirnaturally occurring amounts, herein designated as didymium, is verysatisfactory. These mixtures can be either rich or poor in cerium. Inmany types of didymium the mostfrequently occurring rareearth metals arelanthanum and neodymium, while smaller amounts of praseodymium andsamarium may also be present. In other types of didymium the most minaand may contain, in addition to aluminum oxide, other constituents,provided that the percentage of the other constituents, calculated onthe weight of the total carrier, does not exceed the value of 25 percentby weight. The other constituents may be, for instance, titanium oxide,tin oxide, magnesium oxide, zirconium oxide, thorium oxide, silicondioxide and/or phosphates of aluminium, zirconium,magnesium, titaniumand/or calcium. Preferably, the carrier contains at least percent byweight of aluminum oxide, because a higher content of aluminum oxide inthe carrier is in general attended with a greater activity of thecatalyst, while in addition the special advantages provided by thepresence of the Group Illa modifiers become more prominent.

The specific surface area and the specific pore volume ,of the carriersarenot critical. As a rule, a specific surface area of from 1 to 800 m/g and preferably of from 50 to 700 m /g is preferred. The pore volumeis in general between 0.1 and 0.6 ml/g carrier. The carriers may beprepared by techniques known in the art.

The quantities in which the catalysts are applied may vary within widelimits, the lower limit being set by the minimum quantity that providesjust enough catalytic activity and the upper limit by the maximumquantity that the carrier can support. The maximum quantity mentioneddepends on, among other things, the specific surface area and porevolume of the carrier. In general, quantities of catalysts in excess of0.1 per cent by weight, calculated as metal on carrier, are verysuitable. Usually, the catalysts are applied in a quantity of not morethan 40 per cent by weight and preferably of not more than 20 per centby weight, calculated as total metal on carrier.

In addition to the olefin disproportionation catalyst modified asdescribed above, one or more other components may be present on thecarrier, for example, coactivators, hydrogenating components, componentsfor isomerization of the double bond, and the like.

Cobalt oxide is an example of a coactivator. Thus the combination ofmolybdenum oxide cobalt oxide displays an increased disproportionationactivity. Other suitable coactivators are compounds of iron, nickel, andbismuth, such as iron oxide, nickel oxide and bismuth oxide. The iron,nickel and cobalt coactivators have hydrogenating activity as well.

Some disproportionation catalysts also display hydrogenating activitysuch as catalytic compounds of manganese, palladium, rhodium orruthenium. Other examples of hydrogenating components are manganese,palladium, rhodium, ruthenium, iron, cobalt, nickel and platinum.Suitable metal compounds with hydrogenating activity are, for instance,the oxides, sulphides, ar-allyl or carbonyl derivatives of the abovemetals. In particular, palladium, platinum and nickel and organic andinorganic compounds of these three metals are very suitablehydrogenating components.

The presence of noble metals of Group VIII of the Periodic Table Systemof the Elements may also lead to isomerization of the double bond,particularly when platinum, palladium and ruthenium are present.Palladium is particularly active in this respect. (The termisomerizationd refers to a shifting of the double bond in the moleculewith preservation of the carbon skeleton.)

Coactivators, hydrogenating components and components for isomerizationof the double bond, when utilized, are usually applied in a quantiy,calculated on carrier, smaller than that of the catalyst, for instance,between 0.05 and %w and in particular between 0.5 and 5%w.

The sequence in which the catalyst, coactivators, hydrogenatingcomponents, components for isomerization of the double bondand the GroupIIIa metal are applied on the carriers is not critical; moreover, theuse of co-activators, hydrogenating components and/or components forisomerization of the double bond is entirely optional and may beomitted. The group Illa modifiers may therefore be applied on thecarrier before, after or together with the catalysts, Coactivators,hydrogenating components and/or components for isomerization of thedouble bond. It is also possible to apply first a coactivator, then theGroup Illa metals, then a hydrogenating component and a component forisomerization of the double bond and finally a catalyst.

The application of the various components may be made in anyconventional manner. For instance, the carrier may be impregnated withan aqueous solution of a metal compound and then dried and subjected toa heat treatment. lmpregnation may be effected in several stages withsolutions of the same or different concentrations. Another possibilityis to form an aqueous suspension of the compound to be applied,impregnate the carrier with this suspension and dry the impregnatedcarrier.

The heat treatment of the modified catalyst may be carried out attemperatures between 300C and 750C and for periods ranging from 3 to 10hours. If desired, shorter or longer periods and/or lower and highertemperatures may be applied. Heat treatments in the presence ofnon-reducing inert gases, such as nitrogen, carbon dioxide or helium, orgas mixtures, such as air, as a rule cause an increase in thedisproportionating activity of the catalyst, while heat treatments inthe presence of a reducing atmosphere, such as that of hydrogen ormixtures of hydrogen with an inert diluent such as nitrogen, cause anincrease in the hydrogenatmg activity.

During the heat treatment various changes in the composition arepossible. Thus, cobalt, nitrate and ammonium paramolybdate may beconverted into cobalt oxide and molybdenum oxide, perrhenates may beconverted into rhenium oxide and carbonyl compounds may be convertedinto oxides. Changes in valency during the heat treatment may alsooccur.

If desired, the heat treatment may be carried out in various stagesunder different conditions, while any of the components may be added tothe carrier in the meantime. It is recommended after the last additionto treat the catalyst to remove the free oxygen present in the carrierfor the greater part and the adsorbed water as nearly completely aspossible.

Rhenium heptoxide may be applied to the carrier via a gas phase. To thisend, a hot gas may be passed over heated rhenium heptoxide andsubsequently over the carrier, the temperatures of the oxide, thecarrier and the gas being chosen so that the heptoxide passes to the gasphase and subsequently sublimes onto the carrier. After the sublimationthe catalyst may be activated in a stream of hot air.

The carriers may be applied in any suitable form, for instance aspowders, flakes, pellets, spheres and extrudates.

Reaction Conditions. The disproportionation of the olefinicallyunsaturated compounds can advantageously be carried out at a temperaturebetween 20C350C. At too low temperatures the reaction rate is slow,while at too high temperatures, the pressure required is relativelyhigh. With catalysts containing molybdenum oxide or cobalt oxide, thetemperature chosen is preferably between and 200C, while for catalystscontaining rhenium heptoxide, molybdenum pentachloride or tungstenhexachloride, temperatures between 10 and C, in particular between 20Cand 75C, are very suitable.

In general, the olefinic compounds to be disproportionated will alreadybe present in the feed, that is, passed to the disproportionationreaction. It is, however, possible to cause the formation of theolefinic compounds to be disproportionated to take place in the reactorthrough dehydrogenation of acyclic alkanes. In this embodiment a feedconsisting either partly or entirely of acyclic alkanes is contactedwith a disproportionation catalyst at a temperature of 300 to 500Ceither in the presence or absence of hydrogen. Because at thistemperature disproportionation catalysts actsas dehydrogenationcatalysts, hydrogen is split off from the alkanes or from a partthereof. According to the invention the alkenes thus formed from theacyclic alkanes can be disproportionated in the presence of the hydrogenformed. Disproportionation catalysts containing molybdenum compoundsand/or tungsten compounds are suitable for this specific embodiment ofthe process.

During the disproportionation reaction the pressure may vary betweenwide limits. Pressure from about 0.1 to about 500 atmospheres areacceptable; pressures between 0.5 and 250 atm, in particular between 0.9and 10 atm, are preferred.

The disproportionation may be effected in the presence of both a liquidand a gas phase. If the disproportionation is effected in the liquidphase, the pressure is usually kept at the minimum required to maintainthe liquid phase. When the reaction is effected in the liquid phase forthe reaction components use may be made of solvents or diluents whichunder the specific reaction conditions are inert, such as n-pentane,n-octane, ndodecane, 3-methylpentane, cyclohexane, methylcycloh exane,benzene, and toluene. If the reaction is carried out in the gas phase,gaseous diluents, such as methane, ethane, propane, nitrogen or carbondioxide may be present. Mixtures of diluents, such as mixture ofanaliphatic and an aromatic hydrocarbon may be present. f v

The space velocity at which the ethylenically unsaturated compounds tobe disproportionated are brought into contact with the catalyst is notcritical and may very well vary between 0.1 and 50 liters of compoundsto be disproportionated per liter of catalyst per hour if thedisporportionation is effected in the liquid phase, and between 100 and5000 liters of compounds to be disproportionated per liter of catalystper hour if the disproportionation is effected in the gas phase. Spacevelocities beyond the limits mentioned are not excluded, but are seldomemployed.

In a preferred modification, the process is carried out in the presenceof elemental hydrogen, because the presence of hydrogen imparts to thecatalyst an even longer lifetime and a greater disproportionatingactivity. Another advantage associated with the presence of hydrogen isthat conjugated diene impurities may be present in relatively largeamounts without exerting an adverse influence on the catalyst activity.Hence, a thorough removal of these dienes from the feed to bedisproportionated is not required if hydrogen is present. Althoughlarger or smaller quantities are not excluded, the amount of elementalhydrogen is generally between 0.0] and 150 percent mole, preferablybetween 0.1 and 60 percent mole, calculated on the amount ofethylenically unsaturated compounds to be disproportionated.

The disproportionation may be effected batchwise or continuously in thegas phase or in the liquid phase with fixed catalyst beds, suspendedcatalysts, fluidized catalyst beds, in a reactor provided with astirring device or with application of another conventional contactingtechnique. If desired, the reaction mixture may be separated into threefractions with increasing molecular weights. If the lightest andheaviest fractions contain the products desired, the intermediatefraction may be contacted with a second quantity of disproportionationcatalyst under conditions that are equal to or different from thosewhich prevail during contact with the first quantity ofdisproportionation catalyst, while the two catalysts may be the same ordifferent.

On completion of the disproportionation, one or more of the compoundsobtained may be subjected to a subsequent conversion process.Forinstance, a butenecontaining mixture, formed by disproportionation ofpropene, may be passed, together with isobutane, into an alkylation zonefor the preparation of gasoline com ponents with a high octane number.

The products may be separated by conventional means, such as byisolation from the reaction mixture by distillation, if required underreduced pressure or by separation of the components of the reactionmixture by cooling the mixture and removing the condensed orcrystallized products. Certain fractions,'such as unconverted startingmaterials or fractions in which the number of carbon atoms per moleculediffers from that desired, may be recycled to the disproportionationreactor.

The Products. According to the process of the invention, two olefinicreactants are disproportionated to a product comprising olefin(s) havinga total number of carbon atoms equal to the sum of the carbon atoms ofthe two olefinic reactants and having a number of ethylenic linkagesequal to the sum of the ethylenic double bonds of the reactants.

In the variation of the process which comprises the disproportionationof two molecules of the same olefinic reactant, the reaction of twomolecules of an acyclic olefin of formula (I) generally produces oneolefin of a higher carbon number and one olefin of a lower carbon numberas depicted in equation( 1 2RCR=CHR RCH=CHR R-(IJ=(IJR (1) wherein R hasthe previously stated significance.

The reaction of two molecules of cyclic olefinic reactant of formula(II), however, produces a single cyclic olefin produced as depicted inequation (2) By way of specific illustration, the reaction of twomolecules of cyclooctene produces 1,9-cyclohexadecadiene.

Another variation of the process comprises the disproportionation of twodifferent acyclic olefinic reactants. By way of specific illustration;the reaction of 2- butene and 3-hexene produces two molecules of2-pentene and the reaction of 2-butene with l,4-polybutadiene producestwo molecules of l,4-polybutadiene having a molecular weight which isless than the molecular weight of the starting 1,4-polybutadiene.

Still another variation of the process is ringopening disproportionationwherein an acyclic olefinic reactant represented by formula (I) iscontacted with a cyclic olefinic reactant represented by formula (II).The product of ring-opening is a single olefinic compound with one lesscarbocyclic ring than the cyclic olefinic reactant of formula II. Interms of the formulas I and II, the product is represented by formula(III):

wherein R and A have the previously stated significance. By way ofspecific illustration, from reaction of 2-butene and cyclopentene isproduced 2,7- nonadiene. Other typical products include 2,8- decadieneproduced by reaction of cyclohexene and 2- butene, 3,8-undecadieneproduced from 3-hexene and cyclopentene, 1,5,9-decatriene produced byreaction of ethylene and 1,5-cyclooctadiene, and l,4-divinylcyclohexanefrom ethylene and bicyclo(2.2.2)oct-2- ene.

It is appreciated that an olefinic product produced by any variation ofthe olefin disproportionation process can undergo furtherdisproportionation with another olefin present in the reaction mixture.For example, l,6-heptadiene produced from reaction of cyclopentene andethylene can react with another molecule of cyclopentene to produce1,6,1 1,-dodecatriene, and l,9-cyclohexadecadiene produced from thereaction of two molecules of cyclooctene can react with additionalmolecules of cycloctene to give a high molecular weight monocyclicpolyene.

The products obtained with the aid of the instant disproportionationprocess may be used for various purposes, depending on their molecularweight, the number of double bonds present, the number of carbon atomsbetween the double bonds and the position of the double bonds in themolecule.

Thus, cleavage of the double bonds as caused by ozonization leads to theformation of carboxylic acids. In cases where two or more double bondsare present in the molecule dicarboxylic acids may be formed.Dicarboxylic acids may serve as, for instance, starting materials forthe preparation of polyesters or polyamides from which synthetic fibersare made.

The products, in particular the low-molecular weight products, may, ifdesired after partial hydrogenation, be hydrated according to themethods known in the art to monoor polyhydric alcohols. The products orthe compounds obtained by partial hydrogenation may also be convertedinto alcohols by reaction with carbon monoxide and hydrogen (so-calledhydroformylation or oxonation The alcohols thus obtained are suitable asstarting materials for the preparation of esters which can be used as,for instance, softeners or starting materials for lubricating oiladditives. These alcohols can also be used for the preparation ofdetergents by means of, for instance, sulphation or condensation withethylene oxide or propylene oxide. Polyhydric alcohols in particular arevery suitable for the preparation of alkyd resins and polyurethanes.

To further illustrate the novel disproportionation process and the novelcatalyst composition, the following examples are provided. It should beunderstood that they are not to be regarded as limitations, as theteachings thereof may be varied as will be understood by one skilled inthe art.

Catalyst Preparation. Catalysts were prepared which employed a carrierconsisting of -y-aluminum oxide containing less than 0.5%w of sodium,less than 0.01%w of potassium and less than 0.03%w of calcium. Thecarrier had a pore volume of 0.54 ml/g and a specific surface area of203 m /g. The carrier was first heated at 300C for 2 hours.

Various metals were applied on the carrier by im pregnating the latterwith a volume of an aqueous solution of a compound of these metalscorresponding to 120 percent of the pore volume of the carrier.Subsequently, the impregnated carrier was heated at 120C for 1 hour andheated in air at 500C for 2 hours. The salts of the Group lIla metalsapplied were nitrates. Rhenium was applied by starting from water inwhich rhenium heptoxide was dissolved. All the metals were appliedseparately.

In the Examples the term isopentenes refers to 2- methylbutene-l and2-methylbutene-2.

The two types of didymium mentioned in the Examples had the followingcompositions:

Constituent Type A, %vilype 8, %w Lanthanium oxide n.0,) 42.9 7.7Neodymium oxide (Nd O 36.4 52.3 Praseodymium oxide (Pr On) 1 1.2 9.7Samarium oxide (Sm,0,) 4.9 16.2 Gadolinium oxide Gap 2.4 9.5

Cerium oxide (Ce O 1.5 1.7

Yttrium oxide (Y,O 0.7 2.7

The experiments were performed by passing a gaseous mixture consistingof equimolar amounts of isobutene and 2-butene through a fixed catalystbed at atmospheric pressure, a temperature of l25C, and with a spacevelocity of 1800 liters of gas per kilogram of catalyst per hour. Atspecified times during the reaction, a portion of the product stream waswithdrawn and the conversion of the starting feed of isobutene and2-butene to products (such as pentenes and propenes) determined as amole percentage of the sample at the time the sample was taken. Theselectivity towards isopentenes is calculated on the basis of the totalamount of pentenes formed. The temperature has been chosen high so as todemonstrate the favorable effect of the process with experiments ofrelatively short duration. Even more favorable results would have beenobtained if the experiments had been carried out at a lower temperature,for instance 50C.

In the Tables of the following examples, the amount, measured as moleper cent, of the starting feed converted to products is designated TotalConversion; the mole per cent of the product converted to isopentenesand propenes is designated Conversion into isopentenes and propene; andthe percentage of isopentene in the pentene fraction is designatedSelectivity towards isopentene.

EXAMPLE I The carrier contained 0.25 percent of type A didymium(calculated as metals) and 14.0 percent rhenium (calculated asheptoxide). The gas used as starting material also contained 12.5percent vol of hydrogen. The results are given in Table A.

TABLE A After 1 6 24 hours, mole Total conversion 46.8 32.9 15.9Conversion into isopentenes and propene 44.5 31.6 15.3 Selectivitytowards isopentenes I00 I00 The experiment was repeated with a catalystconsisting exclusively of 14.0 percent w of rhenium heptoxide on'y-aluminum oxide. The results are given in Table B.

TABLE B After 0.5 l 1.5 2.5 hours, mole Total conversion 50.l 36.7 24.04.0 Conversion into isopentenes and 47.7 34.3 21.5 1.5

propene Comparison of the results given in Tables A and B demonstratesthe favorable effect of didymium on the lifetime of the catalyst.

g EXAMPLE n The experiment described in Example I was repeated with theexception that the carrier contained 1.0%w of Type A didymium. Theresults are given in Table C.

TABLE C After 1 6 24 hours, mole Total conversion 45.7 34.0 19.1Conversion into isope-itenes and propene 44.8 33.3 19.1 Selectivitytowards isopentenes 97.7 92.6 86.8

EXAMPLE III The experiment described in Example II was repeated with theexception that the carrier contained 1.5 %w of type A didymium. Theresults are given in Table D.

TABLE D After I 6 24 hours,

mole Total conversion 45.2 30.0 4.7 Conversion into isopentenes andpropene 43.8 28.4 3.7 Selectivity towards isopentens 99 99 99 EXAMPLE IVThe experiment in Example I was repeated with the exception that thecarrier contained 0.25%w of type B The experiment described in ExampleIV was repeated with the exception that the carrier contained 0.5%w oftype B didymium. The results are given in Table F.

TABLE F After 2.5 6 24 hours, mole Total conversion 44.8 33.9 14.4Conversion into isopentenes and propene 43.5' 38.2 14.4 Selectivitytowards isopentenes 100 100 100 EXAMPLE VI The experiment described inExample II was repeated with the exception that the gas used as startingmaterial contained 12.5% vol of nitrogen instead of 12.5% vol ofhydrogen. The results are given in Table G.

TABLE G After 1 '6 24 hours, rnole Total conversion 44.3 28.5 8.6Conversion into isopentenes and propene 42.2 28.5 6.9 Selectivitytowards isopentenes 97.5 99 100 Comparison of the results givin inTables G and F demonstrates that, in the presence of hydrogen, thecatalyst retains its activity over a longer period of time.

EXAMPLE VII The experiment described in Example I was repeated with theexception that the carrier contained, instead of 0.25%w of didymium, 0.5percent, of europium. The results are given in Table H.

TABLE H After 1 3 4.5 hours, vol Total conversion 45.5 35.7 37.0Conversion into isopentenes and propene 43.6 33.2 35.3 Selectivitytowards isopentenes 99 99 99 EXAMPLE VIII The experiment described inExample I was repeated with the exception that the carrier contained,instead of 0.25 percent of didymium, 0.5 percent of cerium. The resultsare given in Table I.

TABLE I After 1 4.5 6 hours, vol. Total conversion 48.3 40.1 35.9Conversion into isopentenes and propene 46.0 38.3 34.7 Selectivitytowards isopentenes 99 99 99 EXAMPLE IX The experiment of Example I isrepeated except that the catalyst is molybdenum oxide containing type Bdidymium. The number of hours the catalyst remains active increases.

EXAMPLE x The experiment of Example I is repeated except that thecatalyst is tungsten oxide modified with 0.5 percent of scandium. Theactive lifetime of the catalyst increases.

We claim as our invention:

1. In the disproportionation of two olefinic hydrocarbon reactants to aproduct comprising olefinic hydrocarbons having a total number of carbonatoms equal to the sum of the carbon atoms of the two olefinichydrocarbon reactants and having a number of v ethylenic linkages equalto the sum of the ethylenic double bonds of the two olefinic hydrocarbonreactants by contacting the two olefinic hydrocarbon reactants at 10 to200C in the presence of an olefin disproportionation catalyst selectedfrom the group consisting of compounds of molybdenum, tungsten andrhenium and mixtures thereof active for olefin disproportionationsupported on a carrier of at least 75 percent aluminum oxide, theimprovement which comprises modifying the olefin disproportionationcatalyst with 0.05 to percent by weight of a modifier selected from thegroup consisting of an element of Group IIIA of the Periodic Tablehaving an atomic number of from 21 to 71 inclusive, compounds thereof,and mixtures of said elements and said compounds.

2. The process of claim 1 wherein the olefin hydrocarbon reactants areacylic hydrocarbon monoolefins of up to 40 carbon atoms, cyclichydrocarbon olefins of up to 4 carbocyclic rings, of up to 12 carbonatoms and up to 3 ethylenic linkages, the carbon atoms of at least oneethylenic linkage being members of a carbocyclic ring of at least fivecarbon atoms and an alkenyl aromatic compound of 8 to 16 carbons havingat least one ethylenic linkage in an alpha position to the aromaticring.

3. The process of claim 1 wherein the olefinic hydrocarbon reactants areisobutene and 2-butene.

4. The process of claim Iwherein the modifier is selected from the groupconsisting of cerium, europium and didymium.

5. The process of claim 1 wherein the disproportionation catalyst isrhenium heptoxide and the modifier is didymium.

6. In the disproportionation of two olefinic hydrocarbon reactants to aproduct comprising olefinic hydrocarbons having a total number of carbonatoms equal to the sum of the carbon atoms of the two olefinichydrocarbon reactants and having a number of ethylenic linkages equal tothe sum of the ethylenic double bonds of the two olefinic hydrocarbonreactants by contacting the two olefinic hydrocarbon reactants at [0 to200C in the presence of an olefin disproportionation catalyst selectedfrom the group consisting of rhenium compounds and mixtures thereofactive for olefin disproportionation supported on a carrier of at leastpercent aluminum oxide, the improvement which comprises modifying theolefin disproportionation catalyst with 0.05 to 5 percent by weight of amodifier selected from the group consisting of an element of Group 111Aof the Periodic Table having an atomic number of from 21 to 71inclusive, compounds thereof, and mixtures of said elements and saidcompounds.

2. The process of claim 1 wherein the olefin hydrocarbon reactants areacylic hydrocarbon monoolefins of up to 40 carbon atoms, cyclichydrocarbon olefins of up to 4 carbocyclic rings, of up to 12 carbonatoms and up to 3 ethylenic linkages, the carbon atoms of at least oneethylenic linkage being members of a carbocyclic ring of at least fivecarbon atoms and an alkenyl aromatic compound of 8 to 16 carbOns havingat least one ethylenic linkage in an alpha position to the aromaticring.
 3. The process of claim 1 wherein the olefinic hydrocarbonreactants are isobutene and 2-butene.
 4. The process of claim 1 whereinthe modifier is selected from the group consisting of cerium, europiumand didymium.
 5. The process of claim 1 wherein the disproportionationcatalyst is rhenium heptoxide and the modifier is didymium.
 6. In thedisproportionation of two olefinic hydrocarbon reactants to a productcomprising olefinic hydrocarbons having a total number of carbon atomsequal to the sum of the carbon atoms of the two olefinic hydrocarbonreactants and having a number of ethylenic linkages equal to the sum ofthe ethylenic double bonds of the two olefinic hydrocarbon reactants bycontacting the two olefinic hydrocarbon reactants at 10* to 200*C in thepresence of an olefin disproportionation catalyst selected from thegroup consisting of rhenium compounds and mixtures thereof active forolefin disproportionation supported on a carrier of at least 75 percentaluminum oxide, the improvement which comprises modifying the olefindisproportionation catalyst with 0.05 to 5 percent by weight of amodifier selected from the group consisting of an element of Group IIIAof the Periodic Table having an atomic number of from 21 to 71inclusive, compounds thereof, and mixtures of said elements and saidcompounds.